While studying polymorphism , i have some doubts that i am unable to clarify ..... Here they are :
Suppose our inheritance ladder be :
C1 <- C2 <- C3 <-....... <- C100
where C1 is most general (superclass) and C100 is most specific class .
Now , if i write java code in my main() :
C21 Obj = new C100();
Obj.someMethod();
So, what will happen in scenarios as given below :
Scenario - 1) If someMethod() is only defined in C1 ? How will compiler search for this someMethod() ?Will it be executed ?
Scenario - 2) If that someMethod() is static and only defined in C1 , then how will it be searched and executed ?
Scenario - 3) If someMethod() is only present in C100 , then what will happen ?
Why is the equals-method in the super-class invoked? Shouldn't the equals-method in the sub-class be invoked(at least in the first if-statement since b2 is a B(i know B is also an A))?Is the equals-method overridden? Or does B have its own equals-method?
class SomeClass{ public static void main(String[] args) {
So, I have a gameOver() method that should when oval goes out of bounds abort game but, as soon as I start the game it runs the gameOver method. I've been looking over it for a while trying different things. I think what stood out to me is removing the abort sequence the game runs mostly as it should after, popup is closed and that if I replace game.gameOver(); with ya = -1 the ball bounces off the wall.
From within that thread I try to call a method from within the same class the contain the thread. This method is not being called. I have confirmed that that section of code is being executed in the thread.
If you look at the following code, the thread being run is called MainThread ln 114, and the method it calls that is not being executed is called onprogressTime() ln 105;
I'm trying to understand the concept behind this recursive method called rangeSum. This method sums a range of array elements with recursion. I tried summing the elements of 2 through 5, and I tried writing down what actually happens when java executes the program, but what I get when I try to figure it out by paper is different from what netbeans gives me. Here is a snapshot of my scratch work as well as my source code. Netbeans gives me "The sum of elements 2 through 5 is 18" when I try running it but it I get 12 when I do the recursion on paper. I know that the source code is correct because it's out of the book but what am I doing wrong when I try figuring it out by hand?
XML Code:
package recursivecall; import java.util.Scanner; /** * Author: <<Conrado Sanchez>> Date: Task: */ public class RecursiveCall {
i am trying to write a coin program:Write a class called Coin which will be used by a program called CountFlips.
1. The class, is an object created from this program. It is composed of data values and methods. It should contain a main method and should output the number of flips done (an integer that will be read from the user), the number of heads and tails that occur.
2. The CountFlip class will flip a coin multiple times and counts the number of ‘heads’ and ‘tails’ that result. This class should have a method called flip() of type void; a method called isHead() of type Boolean and a toString() method that will return the current face of the coin as a string.
So i created 2 classes, one called Coin.java & the other CountFlips.java,
PHP Code: package test; public class Coin { private final int heads = 0; private final int tails = 1; private int facetype; private int flips;
Write an instance method, contains, that has one explicit parameter of type Rectangle. The method should return true if every point of the rectangle determined by the explicit parameter is on or within the rectangle determined by the implicit parameter. It should return false otherwise.
i have to "Write a method called addToOverThirty which takes the array nums3 as a parameter. It adds 1 to all numbers that have a value greater than 30 in the array.
Add a call to the addToOverThirty method, then display a message telling what the output is followed by the results For example:The nums3 array after adding 1 to all numbers greater than 30 is10 6 15 and so on (check with the values you assigned to nums3)"its pointless because we were told not to make the array have a number over 30.
import java.lang.*; import java.util.*; public class LastProject public static void main(String[] args) { int nums1[] = new int[15]; int nums2[] = new int[15]; int nums3[] = {5,2,15,8,26,22,1,29,4,23,30,11,19,6,24};
Create a method called mirrorImage, which takes two integer arrays as input parameters. You may assume that the two actual parameters have the same length. Your method should return true if the arrays are the reverse of each other. Otherwise mirrorImage should return false.
Examples:
data1:{1,2,3} data2:{3,2,1} ==> true
[code].....
I'm pointing a place outside of the array or something
I'm working on a banking program that is supposed to use 3 classes (Account-base class, CheckingAccount, and SavingsAccount) and several methods to display the banking information (ID, balance after a withdrawal and deposit, and the annual interest rate). This should be a pretty simple program, but I'm getting hung up on one portion of it. I'm getting some compiler errors, all of which deal with non-static variables being called from a static context (I'll also post these errors following the code). Up until the middle of last week, we just declared everything as static, but that's changed and I'm having trouble figuring out when to and when not to use static when declaring my methods, hence the compiler errors.
import java.util.Date; public class Account { private int id = 0; private double balance = 0; private double annualInterestRate = 0; private Date dateCreated = new Date();
[Code] ....
Here are the compiler errors I am receiving:
Compilation completed. The following files were not compiled: 6 errors found: File: C:UsersHiTechRedneckDesktopSummer II 2014Computer Programming PrincipleProgram 5CheckingAccount.java [line: 7] Error: non-static method getId() cannot be referenced from a static context
I have a program I want to make (text based, no gui). There is the main class, an Employee class (sort of a template), a CrewMember class, and a Manager class.
I'll put the code for each class an explain the problem I have.
package polymorphism; import java.util.Random; public class Start { public static void main(String[] args) { Random rand = new Random(); Employee staff[] = new Employee[5]; for(int i = 0; i < staff.length; i++){
[Code] ....
Some of the code is a bit incomplete simply because I ran into the problem. As you can see I made an array in the Start class and it holds objects of Employee type, but create a new instance of either a crew member or a manager, sets their wages, hours, and bonus if applicable. I know if I create an array of a certain type, I can't call upon the subclass' method (Manager in this case) because it has a new method that I added. What I'm trying to do is pretty much call upon the getSalary() method in the Manager class/object, but of course I can't. What way would i be able to do that? I tried looking for some answers. I read about making the superclass abstract and implementing it into the subclasses. Would that be an option?
Recently I have been thinking of using additional interfaces in one of my libraries to hide certain "unsafe" methods of my classes from the user. I would like to get the opinion of other, more advanced java programmers on this issue. What I do is something like the following (heavily simplified):
public interface ReadOnly { public int getValue(); } public interface ReadWrite extends ReadOnly { public void setValue(int value);
[Code] ....
The user would have access to the ExternalInterface. The ExternalInterface is controlling the values of the InternalComponent. The user can get the InternalComponent, but typecasted to a ReadOnly which does not expose the setters.
Now the thing is the user can still access the setValue method by typecasting the ReadOnly to an InternalComponent or to a ReadWrite, and that is not bad. If the user knows exactly what he/she is doing this will give him/her more flexibility and more power. But this way it *should* become obvious that this is not the intended use and perhaps the extra work of typecasting will discourage the user from doing this.
I have a quick polymorphism question. I have a parent class and a sub class that extends the parent class. I then declare an array of parent class but instantiate an index to the sub class using polymorphism. Do I have to have all the same methods in the child class that I do in the parent class? Here is an example of what I mean.
public class ParentClass { public ParentClass(....){ } public String doSomething(){ } } public class ChildClass extends ParentClass { public ChildClass(....)
[Code] ....
Is polymorphism similar to interfaces where the child class needs all the same methods?
I am working on a project that uses a custom tag in a JSP file. Here is the tag descriptor
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd"> <taglib> <tlibversion>1.0.0</tlibversion> <jspversion>1.1</jspversion>
[code]...
Everything seems working fine except that the custom tag handler does not get called at call. I set breakpoint and it never stops there. The JSP page is displayed fine, only not showing the custom tag content and there is no logged error/warning from the log. The tld is found fine. Like what classes called/validated the tag handler so I can logging those classes at DEBUG level to see what goes wrong.
In my pursuit to modify the tutorial Android application Bluetooth Chat, I'm trying to add View Switcher to alternate between screens simultaneously in the app, but in my function onCreate ViewSwitcher isn't being resolving and I get a debugging error when trying to run the app. The spelling match and all required libraries are being called, so not sure how to fix it. My code for onCreate function is:
@Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); if (D) Log.e(TAG, "+++ ON CREATE +++");
// Set up the window layout setContentView(R.layout.main);
I just wanted to know that why are final and abstract called as modifiers ,what is the essence of calling them as modifiers since there are two types of modifiers access modifiers and non-access modifiers so final and abstract come under the second category ,so why are these called as modifiers?
Write a program called GeometricMean that prompts the user to
1.Enter the number of values (total number of instances) that should be processed
2.A set of values to be processed (in a while loop)and then calculate the geometric mean of the values entered. You should use a while loop to perform the multiplication part of the calculating the geometric mean. The program should output the initial data and the labeled geometric mean. Consider printf, and DecimalFormat.
My Program:
import java.util.Scanner; public class GeometricMean{ public static void main(String[] args) { Scanner keyboard= new Scanner(System.in);
We have to create a program called MyStack.In Push: Add one element at the end of the buffer.In Pull: Remove one element from the end of the buffer. In isEmpty: Should check if the list is empty or not and return the result as a boolean variable.
I am totally confused, I wrote the buffer and the array, but how do i add an remove element from the buffer?How do i add an element? What Statement do i Use?
Java Code: public class MyStack<T> implements Stack<T> { private final T[] ringbuffer; int index = 0; int last;
I am making a simple battleship program, you have the menu and click Start to get the board with the bombs (4 buttons as of now) Each button has either a bomb or a defualtbutton. I created my button so it can't be unselected. The problem is I have the button in a Class.java and I want that to close in a period of time. What do you recommend using?
/* * To change this license header, choose License Headers in Project Properties. * To change this template file, choose Tools | Templates * and open the template in the editor. */ package battleship; import java.awt.Dimension; import java.awt.EventQueue; import java.awt.GridBagLayout;
[code]....
I can call the clas in my main jFrame but I want to close the class after a certain time.
